The next time to evaluate your shop will be October 1st, so they will be looking at the months of July, August and September. Be aware though that sometimes messages in the last few days of the month don't always count.
from the help page
"Messages sent on the last two days of the 3-month review period may be excluded from the current review period and counted towards the next period instead. This is to allow Sellers a full 24 hours to respond and not be penalized for messages received late on the final day of the review period."
